Field of the Invention
The invention relates to a set-top box (STB), and more particularly to a format conversion circuit applied to an STB.
Description of the Related Art
In the recent years, some image signal use a high dynamic range (HDR) format. Compared to a conventional standard dynamic range (SDR) (e.g., in a range of 0 to 1000 nits), an HDR (e.g., in a range of 0 to 10000 nit) can provide an image with higher contrast and clearer image. Because not all current televisions support the HDR format, a set-top box (STB) coordinating with a television may convert received image signals to image signal having a format supported by the television; that is, the STB can convert the image signals from an HDR to an SDR or convert the image signals from an SDR to an HDR. However, even if an STB can convert image signals to a format that can be played by a television, a maximum luminance value outputted by the STB may differ from a maximum luminance value that can be displayed by a display panel of the television, resulting degraded image display. Further, even if a television has a luminance adjustment function, display quality is nonetheless affected if the adjustment function is inadequate.